cubic yards of soil that had to be removed to make
way for the foundations,” Grenz explains, who
estimates there was enough dirt removed from the
site to fill around 300 Olympic size swimming pools.
Sitting on foundations running between 45-60ft
(13-18m) deep, the stadium is built around eight
cores, attached to 16.5-miles of steel pilings. The
project was one of the biggest steel jobs in the US (it
required the use of two of the largest cranes in North
America among a fleet of 18), with over 20,000
individual pieces of structural steel to affix into a
nest-like array.
The stadium is made up of two independent
structures – the bowl section and the outer vessel,
which is formed of big steel trusses and cantilevered
trusses over the bowl connected to the roof section.
This ensures resistance against any high wind or
seismic effects that allow the building to shift on
spherical bearings and accommodate any movement
to prevent cracking. All of this had to be done with
a margin of error at .00006% with teams using GPS
systems to accurately pin-point the position of the
steels, but the high heat presented another challenge.
“There was a constant surveying of the structure
because in Las Vegas when you erect one part of the
building the temperature might be 110F and when
you get to erecting the last section the temperatures
might only be as high as 60F so we’re having to
constantly measure the expansion and contraction
of the structural steel system to accommodate various
deformation cases might be,” describes Grenz.
stainless
steel cables
create the roof
ALLEGIANT STADIUM
CLEAR VISION
structure
diaphragm
The roof at Allegiant Stadium takes the form of a
flat dome consisting of 107 individual ETFE
cushions measuring approximately 15ft x 200ft
(4.5 x 60m) each. The cushions are supported
by 1,300 tons of secondary steel and together
create a surface area of 350,000ft² (32,516m²).
“We were amazed by the ingenuity of the initial
design concept where a
futuristic visual approach is in
symbiosis with superior
material properties,” explains
Alexander Jafari, project
executive at Vector Foiltec,
who supplied the ETFE roof.
“A roof concept like this, of
this scale, had never been
constructed before. Our
design and delivery was
divided into fi ve phases
starting with design assist
where the overall concept,
cushion sizes, and structural
system were defi ned. This was
followed by the design
process where our highly
experienced in-house team
turned the architect’s vision
into a feasible solution. The
fabrication of the ETFE
materials took place in
Bremen, Germany, and the
steel was fabricated near
Venice, Italy. To mitigate any
delivery risk, both the ETFE
and steel system was
delivered six months ahead of
their scheduled installation.
The erection of the roof went
quite smoothly. The steel
structure was installed within
four weeks and the Texlon
ETFE system followed in just
under six weeks,” says Jafari.
100
“In certain phases in erection of the steel we always
knew that there would be deformation of that structure
so we had to get deformation cases where you had to
wait before we could construct other parts such as the
curtain wall,” he adds.
The heat also had an effect on how concrete
activities and the workers schedules were carried out
with many pours being performed at night or during
the very early hours of the morning to avoid high
daytime temperatures. Workers, who would start shifts
early and leave the site by around 1pm, were
encouraged to take frequent rehydration breaks at
cooling stations setup around the site.
While running the risk of acting like a big terrarium
in the desert, the stadium also beats the heat with a few
smart tricks. Firstly, it sits below grade which helps
keeps the bowl cooler and its black glass curtain wall
actually aids with cooling, as well as being conveniently
on-brand for the team.
“I’ve heard people joke about putting a black
stadium in the middle of the desert, but the truth is
black glass is the very best kind we could have put on
it from an air conditioning standpoint. It keeps the
building as cool as possible, and the blacker the better,”
says Manica. “It was an intentional decision to save
money and save on cooling. We went through
additional tinting and fritting to control the amount
of heat gain and to meet the energy requirements of the
current code, which are quite stringent. It produces an
amazing soft light inside that’s really comfortable, even
if its 104-degrees outside”.
www.stadia-magazine.com June 2020 21
/www.stadia-magazine.com